I Samuel 17:33
Then Saul said to David, “You are not able to go against this Philistine to fight with him; for you are but a youth while he has been a warrior from his youth.”
David had to answer Saul's concern. He didn't and wouldn't understand. It's a matter of faith. To tell unbelievers reasons why we do things in faith won't be received. I Corinthians 2:14 says, "But the natural man does not accept the things of the Spirit of God; for they are foolishness to him, and he is not able to understand them, because spiritually they are discerned."
I don't believe we normally share these dreams with an unbeliever. Their doubts could weaken our faith. Saul's argument was reasonable. It was a great reason for David to not engage the giant. However, David's motivation to face Goliath was of faith.
Sometimes the Lord wants us to do things that aren't reasonable. 2 Corinthians 5:7 says, "we walk by faith, not by sight". David knew the Lord had prepared Him for this fight. The practice runs were the lion and the bear. His brothers may have also given him grief. He may have had to learn to manage bullies in his own home.
To David, this fight was reasonable. It was almost the normal progression. Not so with the worldly mind. It didn't make sense. The Lord does works of faith with us. He will lead us and guide us with the smaller circumstances. Next we will have big things. To try to explain to an unbeliever would not be understood.
Much of what Jesus said was in parables. The crowds wouldn't get them. However, a percentage goes further and wants more. Some times the Lord wants us to share these things. They are usually seeds to be planted. Sometimes they grow other times not. Sometimes we witness the growth, most times it's internal.
We were once in the unbelieving camp. The Lord drew us and others shared things. In time we accepted it. However, there were times when we weren't quite ready. I can recall getting offended when witnessed to. A year later I understood and wished I could have apologized.
If we are in Christ, our eyes were opened at some point. 2 Cor 4:4,5 gives some insight, "The god of this age has blinded the minds of unbelievers so they cannot see the light of the gospel of the glory of Christ, who is the image of God. For we do not proclaim ourselves, but Jesus Christ as Lord, and ourselves as your servants for Jesus’ sake." The message of Jesus opens eyes. Paul says "we do not proclaim ourselves", which means they don't use clever arguments or reason. Just Christ.
We are to walk in obedience and share with those who come in our path. We aren't to be concerned with how it's received. David was asked and he answered. Saul didn't understand. It's interesting that he let David proceed. Maybe the Lord gave him some insight.
Lord, thank You for partnering with us in this life of faith. What an honor that You do so. Help us to grow in discernment. Help us not to let the worldly mind corrupt us, but boldly share when You want us to.